1. Communication Between Camel Routes
JB Onofré

2. Agenda Background Why multiple routes ? Local communication
Remote communication
Q&A

3. Who I am Jean-Baptiste (JB) Onofré <jbonofre@apache.org>
ASF Member
PMC for Karaf, ServiceMix, ACE, Syncope, ...
Committer for Camel, Archiva
Software architect at Talend (

4. Divide to reign (Game Of Code, CamelOne 2013)
Why multiple routes ?
A route is a …
So it can be ...
Divide to reign (Game Of Code, CamelOne 2013)

5. Benefits of multiple routes
Reuse of existing routes
Maintain “atomic” routes by different teams
Each route has its own life cycle (provisioning, upgrade of a route without impacting another one, …)
Easier to test (utests and itests)
Scalable on multiple machines (remote)

6. Communication between local routes – Direct
Direct component (camel-core)
Synchronous
Local to the same Camel context
Machine
CamelContext
Route1
Route2

7. Communication between local routes – Direct
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”direct:route2”/>
</route>
<route id=”route2”>
<from uri=”direct:route2”/>
<to uri=”stream:out”/>
</camelContext>
</blueprint>

8. Communication between local routes – Direct-VM
Direct-VM component (camel-core)
Extension of the Direct component (Synchronous)
Communication between routes from different CamelContexts
Machine
CamelContext1
CamelContext2
Route1
Route2

9. Communication between local routes – Direct-VM
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”direct-vm:route2”/>
</route>
</camelContext>
</blueprint>
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route2”>
<from uri=”direct-vm:route2”/>
<to uri=”stream:out”/>
</route>
</camelContext>
</blueprint>

10. Communication between local routes – SEDA
SEDA (Staged Event-Driven Architecture) (camel-core)
Asynchronous
Use JVM BlockingQueue on the Producer
Different thread on the consumers (possible to have multiple consumers)
Machine
CamelContext
Route1
Route2
BlockingQueue

11. Communication between local routes – SEDA
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”seda:route2”/>
</route>
<route id=”route2”>
<from uri=”seda:route2”/>
<to uri=”stream:out”/>
</camelContext>
</blueprint>

12. Communication between local routes – VM
VM component (camel-core)
Extension of the SEDA component (Asynchronous)
Communication between routes from different CamelContexts
Machine
CamelContext1
CamelContext2
Route1
Route2
BlockingQueue

13. Communication between local routes – VM
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”vm:route2”/>
</route>
</camelContext>
</blueprint>
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route2”>
<from uri=”vm:route2”/>
<to uri=”stream:out”/>
</route>
</camelContext>
</blueprint>

14. Communication between routes
Camel provides components for local routes communication
Direct/direct-vm: synchronous
SEDA/VM: asynchronous
Different ways for remote routes communication. For this presentation:
REST (CXF RS): synchronous
JMS (ActiveMQ): asynchronous
Hazelcast (Cellar): asynchronous

15. Remote communication between routes – REST
RESTLET component (camel-restlet, but can use CXF)
Synchronous
Similar to direct but in remote
Machine
Machine
CamelContext
CamelContext
Route1
Route2

16. REST <?xml version=”1.0” encoding=”UTF-8”?> <blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:fire?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”restlet:
</route>
</camelContext>
</blueprint>
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route2”>
<from uri=”restlet:
<to uri=”stream:out”/>
</route>
</camelContext>
</blueprint>

17. REST – Pros/Cons Pros: Cons:
Directly supported in Camel thanks to the camel-restlet or camel-cxf components
Very easy to use (especially with RESTLET)
Support load balancing (for instance mod_proxy_balancer)
Similar to direct but in remote
Cons:
Overhead depending of the data format
Order of startup (error handling)

18. Remote communication between routes – JMS
JMS component (camel-jms)
Async
Machine
ActiveMQ
Machine
CamelContext
CamelContext
Route1
Route2
Queue

19. ActiveMQ JMS <?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”jms:queue:route”/>
</route>
</camelContext>
</blueprint>
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route2”>
<from uri=”jms:queue:route”/>
<to uri=”stream:out”/>
</route>
</camelContext>
</blueprint>

20. JMS – Pros/Cons Pros: Cons: Support important load
Support advanced features: messages persistence, network of brokers, master/slave
Cons:
Require an additional middleware (ActiveMQ)

21. Remote communication between routes – Karaf Cellar/Hazelcast
Hazelcast component (camel-hazelcast)
Async (SEDA)
Leverage Karaf Cellar (powered by Hazelcast)
Machine
Cellar/Hazelcast
Machine
Cellar/Hazelcast
CamelContext
CamelContext
Route1
Route2
DataGrid

22. Karaf Cellar ? Apache Karaf subproject
Each node embeds Hazelcast instance (no point of failure)
Provides data grid and cluster events
Used for “clustered provisioning”

23. Karaf Cellar Architecture
Hazelcast
Hazelcast
Cellar
Cellar
Cluster Event Consumer
DataGrid
Cluster Event Consumer
Cluster Event Handler
Cluster Event Handler
Cluster Event Producer
Cluster Event Producer
Synchronizer Local listeners
Synchronizer Local listeners
Shell commands MBeans
Shell commands MBeans
Local resources (bundles, features, config)
Local resources (bundles, features, config)

24. Karaf Cellar Components
Cluster event producer: creates a cluster event and broadcast it to the other cluster nodes
Cluster event consumer: receives a cluster event and delegates the handling
Cluster event handler: handles a specific cluster event (bundles, features, config, …)
Synchronizers: call at the Cellar bootstrap to synchronize the local node state with the cluster state
Local listeners: listens for local resource events (bundles, features, config, …), and creates a cluster event sent to the other nodes
Shell commands (cluster:*)/MBeans: manipulate resources on the cluster

25. Karaf Cellar and Camel
Cellar provides Hazelcast support in Karaf, including classloader handling, configuration support (installing etc/hazelcast.xml), …
Camel-hazelcast component uses the Hazelcast instance provided by Cellar

26. Hazelcast <?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route1”>
<from uri=”timer:simple?period=5000”/>
<setBody>
<simple>Hello CamelOne</simple>
</setBody>
<to uri=”hazelcast:seda:route”/>
</route>
</camelContext>
</blueprint>
<?xml version=”1.0” encoding=”UTF-8”?>
<blueprint>
<camelContext>
<route id=”route2”>
<from uri=”hazelcast:seda:route”/>
<to uri=”stream:out”/>
</route>
</camelContext>
</blueprint>

27. Hazelcast – Pros/Cons Pros: Cons:
Similar to SEDA but for remote communication
No equirement to use an external middleware (Cellar)
Support Hazelcast advanced features: discovery/multicast, cache persistence, near cache, enviction, ...
Cons:
Not really used :(

28. So ... It's good to split a big route into sub-routes
Camel directly supports local route communication
But Camel provides a set of components that allows you to communicate with remote routes
Thanks to remote routes communication, you can implement a distributed architecture

29. Thank you ! Questions ? Keep in touch: twitter: @jbonofre e-mail: jbonofre@apache.org